The invention relates to a sub-band splitter unit and an envelope curves detector provided with a sub-band splitter unit. A sub-band splitter unit according to the preamble of claim 1 is known from U.S. Pat. No. 5,235,647. This known sub-band splitter unit operates together with an associated sub-band combining unit for combining the K narrowband sub-band signals of the sub-band splitter unit for generating a broadband output signal that is a replica of the broadband input signal of the sub-band splitter unit.
In the known sub-band splitter unit, the broadband input signal is, by means of down-sampling, converted into narrowband (subsampled) sub-band signals, and, in the sub-band combining unit, these narrowband sub-band signals are, by means of up-sampling, converted back into a replica of the input signal with the same sampling rate as the one of input signal.
The sub-band splitting unit known from U.S. Pat. No. 5,235,647 includes sub-band filter circuits for generating the K narrow-band sub-band signals. The sub-band combining unit cooperating therewith also comprises filter circuits for combining the K narrowband sub-band signals for generating the replica of the broadband input signal of the sub-band splitter unit. U.S. Pat. No. 5,235,647 proposes to select the filter length of the filter circuits in the sub-band splitter unit unequal to the filter length of the filter circuits in the sub-band combining unit. It is thereby achieved that, for example, the complexity of the signal processing in the sub-band splitter unit be selected greater and the complexity of the signal processing in the sub-band combining smaller, for example, at constant transmission quality of the transmission path between the input of the sub-band splitter unit and the output of the sub-band combining unit.